If you were a right-hander, your muscle group on your right would be bigger. Your spine requires both sides of muscle to keep it in place and since one side is larger, there will be some rubbing, thus creates friction. As time goes by, there will be some wear and tear.
The way you stand or walk might be wrong and that you might be only using the muscle on your back waist. Therefore, when your back muscle is injured, your waist cannot support your upper body, causing pains. The correct posture will require both the back and abs muscle to maintain your body weight.
In order to rectify the two problems, train up your left body muscle to keep it balance and also train up your abs muscle so that your back muscle can rest to recuperate.
Remember that the muscle by the side of your spine is used only for supporting the spine, do not over exert it by bending forward to carry heavy loads or by other means.